1. Field of the Invention
The present invention relates to a slide bearing, and particularly, to a slide bearing capable of providing sufficient performance when used in a housing which has recently come to be formed by use of aluminum in order to reduce the level of fuel consumption and the weight of internal combustion engines, and which has also come to be subjected to increased force of inertia as internal combustion engines have been adapted to achieve higher speeds or greater numbers of revolutions per unit time.
2. Description of the Related Art
A conventional slide bearing for use in an internal combustion engine comprises a steel back-metal layer, a copper-alloy layer and a lead-alloy overlay. Known examples of materials for forming the copper-alloy layer include Cu--Pb alloys and Cu--Sn--Pb alloys. Known examples of materials for forming the lead-alloy overlay include Pb--Sn alloys, Pb--Sn--Cu alloys, and Pb--Sn--In alloys.
Regarding materials for forming the steel back-metal, low carbon steels containing not more than 0.20% by weight of carbon have been normally used. Almost all such conventional steel back-metals have a 0.01% elastic limit of non more than 300 N/mm.sup.2.
In recent years, in an internal combustion engine, engine blocks, connecting rods, etc. have increasingly been made by using aluminum alloys. Thus, the housing of an internal combustion engine has come to be formed by use of aluminum alloys. As a result, the housing is more likely to deform than conventional housings made of cast iron, carbon steel or alloy steel when subjected no force of inertia during a high-load operation of the engine or an operation thereof with a great number of revolutions per unit time. Deformation of the housing impairs tight contact between the housing and a bearing, thereby causing fretting (surface damage occurring when slight relative movement is repeated between two faces contacted each other) or migration (local concentration of Cu plating, flash plating and/or carbide which local concentration occurs due to the repetition of relative movement), which may in turn cause damages, such as fatigue or seizure, or unwanted co-rotation with a shaft. In order to avoid these risks, it is necessary to form the steel back-metal of the bearing with a hard, high strength material, and to employ an large interference when assembling the bearing onto the housing, to thereby improve the tight-contact ability of the bearing.
However, a conventional back-metal made of a low carbon steel cannot have sufficient strength in a case where the back-metal is subjected to only rolling during the preparation a bimetal for the bearing. On the other hand, when a slide bearing is assembled on a housing with an increased interference, the bearing may be subjected to stress exceeding its elastic limit, resulting in permanent strain in the bearing. Thus, it has not been possible to achieve sufficiently satisfactory results.